For over 10 years, services to prevent maternal to child HIV-1 transmission (PMTCT) have been scaled-up and integrated into antenatal care in the national health system across Mozambique. In 2004, scale-up of anti-retroviral treatment (ART) also began in Mozambique and is now provided at hundreds of health units. Recent clinical research has shown that provision of ART to HIV-positive women early in pregnancy substantially reduces risk of HIV virus transmission to the infant. As a result, in 2010 the World Health Organization developed new treatment guidelines that emphasize early initiation of ART in antenatal care for all HIV-positive pregnant women. Those with CD4 d350 cell/mm3 initiate ART as therapy for life, while those with CD4>350 should start ART in ANC as prophylaxis and discontinue treatment after cessation of breastfeeding. The new guidelines have been adopted by the Ministry of Health in Mozambique but not yet implemented. As in many African settings, numerous bottlenecks in health system patient flow present major challenges to successful adoption of the guidelines. ANC and HIV testing coverage is high but there is substantial loss-to-follow-up (LTFU) at successive stages in the treatment cascade. Only a small proportion of eligible HIV-positive pregnant women in Manica and Sofala Provinces manage to initiate ART. Delays in CD4 test results, subsequent preparatory visits, and inadequate counseling contribute to high LTFU. The successful implementation of new WHO guidelines therefore requires major streamlining of links among ANC, PMTCT, and ART services. The overall objective of this project is to develop and test a pilot intervention in central Mozambique to implement the new WHO guidelines and increase the proportion of HIV-positive pregnant women in target ANC clinics who start ART prior to delivery, without reducing ART adherence. The intervention will emphasize a test and treat approach; HIV-positive mothers will initiate ART at the time they receive a positive HIV test result in their first ANC visit, while CD-4 test results and patient-centered adherence counseling will be provided and managed in ANC after treatment initiation. The project will use implementation science techniques to develop and test the intervention.